Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$159.76	5.195%	$168.0595	$168.06	$168.05	$168.10
Purchase #2	$31.52	10.820%	$34.9305	$34.93	$34.95	$34.90
Purchase #3	$192.66	9.566%	$211.0899	$211.09	$211.10	$211.10
Purchase #4	$196.32	6.320%	$208.7274	$208.73	$208.75	$208.70
Purchase #5	$162.44	12.543%	$182.8148	$182.81	$182.80	$182.80
Purchase #6	$152.74	9.422%	$167.1312	$167.13	$167.15	$167.10
Purchase #7	$89.69	12.122%	$100.5622	$100.56	$100.55	$100.60
7 purchase totals =	$985.13		$1,073.3155	$1,073.31	$1,073.35	$1,073.30